The manufacture of unsaturated polyester resins (UPR) is well known in the art. Unsaturated polyester resins are obtained by the condensation reaction of one or more of a saturated di- or polycarboxylic acid or anhydride and an unsaturated di- or polycarboxylic acid or anhydride with a glycol and/or a polyhydric alcohol. The unsaturated polyester resin can also be prepared from unsaturated di- or polycarboxylic acid(s) or anhydride(s) with glycols and/or polyhydric alcohol(s). The traditional known unsaturated polyester resin solution also contains ethylenically unsaturated monomer. The ethylenically unsaturated monomer can be any ethylenically unsaturated monomer capable of crosslinking the unsaturated polyester resin via vinyl addition polymerization. Examples of useful ethylenically unsaturated monomers are styrene, o-, m-, p-methyl styrene, methyl acrylate, methyl methacrylate, t-butylstyrene, divinyl benzene, diallyl phthalate, triallyl cyanurate and mixtures of two or more unsaturated monomers. The preferred monomer is styrene because it provides an economical monomer solution. Conventional unsaturated polyester resin usually contains 35 to 45 wt % of styrene and other volatile organic compounds (VOC).
The presence of large amounts of styrene in such resin compositions results in the emission of styrene vapors into the work atmosphere which constitutes a hazard to the environment. In view of this environmental hazard, governments have established regulations setting forth guidelines relating to volatile organic compounds which may be released to the atmosphere. The U.S. Environmental Protection Agency (EPA) has established guidelines limiting the amount of styrene released to the atmosphere, such guidelines being scheduled for adoption or having been adopted by various states of the United States. Guidelines relating to styrene, such as those of the EPA, and environmental concerns are particularly pertinent to the composite industry which uses styrene that is emitted into the atmosphere.
To reduce styrene and VOC content in unsaturated polyester resins, researchers have tried to develop low VOC resin compositions in which the VOC in the resin is kept at the lowest possible level. One way to reduce VOC is to reduce the molecular weight of the resin. According to polymer physics theory, the viscosity of polymers in the liquid state depends mainly on the average molecular weight, so it is desirable to reduce average molecular weight for a low VOC product. Low molecular weight leads to a lower viscosity and lower styrene need. Compared with conventional resin, which has higher molecular weight and higher styrene content, the low VOC resin typically contains 35% or less styrene and VOC content. The lower molecular weight resin has the advantage of reduced VOC, but it also has disadvantages over the conventional resin. The lower molecular weight resin tends to have poor properties such as low mechanical properties and high hydrolysis in applications compared to the conventional resin.
The production of thermoset polymers by ring-opening metathesis polymerization (ROMP) of cycloolefins is well known in the art. Many US and foreign patents and literature references relate to the ROMP of dicyclopentadiene (DCPD) in the presence of a variety of olefin metathesis catalyst systems. The earlier ROMP process involved the use of a multiple-component catalyst system. The ROMP catalyst and activator were dissolved in different reactant streams, and the various reactant streams were combined to form thermoset polymers during the molding process. U.S. Pat. No. 4,426,502 describes a tungsten or molybdenum compound catalyst and an alkoxyalkylaluminum halide or aryloxyalkylaluminum halide co-catalyst to polymerize the cyclic olefins by a reaction injection molding (RIM) process at an elevated temperature in a period of less than about 2 minutes. U.S. Pat. No. 4,469,809 describes a two-part metathesis catalyst system containing WOCl4, WCl6 or a combination of WCl6 plus an alcohol or phenol as the metathesis catalyst. A second part of the catalyst system is comprised of an activator such as SnBu4, AlEt3, AlEt2Cl, AlEtCl2, or similar compounds. The activator also contained a solution including an ester, ether, ketone or nitrile, which serves to moderate the rate of polymerization. U.S. Pat. No. 4,923,936 describes a catalyst and co-catalyst system containing organoammonium, organophosphonium, and organoarsonium heteropolymolybdates and heteropolytungstates as catalyst and alkylaluminum, alkylaluminum halides, alkoxyalkylaluminum halides, aryloxyalkylaluminum halides as the co-catalyst. U.S. Pat. No. 5,194,534 describes a two-component ROMP catalyst system containing a pure tungsten-imido compound and an activator compound selected from organometals and organometal hydrides.
However, in the reaction using a multiple-component ROMP catalyst, the monomer must be highly purified, and catalyst poisons such as water and alcohols must be avoided. U.S. Pat. No. 5,296,566 describes a one-component transition metal-containing catalyst system which is air and moisture stable. The one-component catalyst is a cationic organometallic ruthenium and osmium-containing salt having at least one polyene ligand. U.S. Pat. Nos. 5,312,940, 5,342,909, and 5,831,108 disclose a ruthenium or osmium carbene complex catalyst useful as a one-component catalyst in ROMP, which is particularly useful in the living polymerization of strained and unstrained cyclic olefins. This type of ROMP catalyst is stable in the presence of various functional groups and is less sensitive to the catalyst poisons present in the lower purity monomer. U.S. Pat. No. 6,020,433 describes using the ruthenium or osmium carbene complex catalyst to make poly DCPD from lower grade DCPD (contains 81-86% DCPD monomer) starting materials. The lower grade DCPD may contain the impurity of various functional groups including hydroxyl, thiol, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, and halogen. The activity of one-component ROMP catalyst can also be improved by adding a second component. U.S. Pat. No. 6,147,026 shows that the addition of hydroxyl group-containing 1-alkynes increases the catalytic activity of the ruthenium and osmium phosphines very substantially and improves the properties of the polymers considerably.
The ROMP catalyst system may also include other type initiators to improve the properties of the thermoset polymer. U.S. Pat. No. 4,835,230 describes a multi-component ROMP catalyst system including a metathesis catalyst, an activator of the metathesis catalyst, a moderator, and a cationic polymerization initiator. The thermoset dicyclopentadiene polymers and copolymers made with this multi-component ROMP catalyst system have higher Tg and HDT and lower residual monomer content. U.S. Pat. No. 5,268,232 describes a molded article comprising the ROMP reaction product of a mixture DCPD monomer and norbornene group containing cycloolefins in the presence of a metathesis catalyst and a co-catalyst that is capable of crosslinking the unsaturated double bonds. U.S. Pat. No. 5,728,785 includes a one-component ruthenium or osmium carbene complex ROMP catalyst in the presence of a modifier or cross-linking agent. Polymer with very high cross-linking density can be produced with the catalyst system. A lower purity cycloolefin monomer (e.g., 85-95% dicyclopentadiene (DCPD)) can also be polymerized to form a highly crosslinked material. U.S. Pat. No. 6,204,347 uses a ROMP catalyst of ruthenium compound and a tertiary phosphine containing at least one secondary alkyl radical or cycloalkyl radical bond to the phosphorous atom to cure a strained cycloolefin.
A wide range of unsubstituted and substituted cycloolefins have been employed as monomers in the ROMP. These unsubstituted and substituted cycloolefins include mono-cyclic olefins, bicyclic olefins, polycyclic olefins and heterocyclic monomers. The substituents are primarily a hydrocarbon group such as alkyl, cycloalkyl or aryl radicals. Functional groups are also possible as substituents in cycloolefins. The heterocyclic monomers contain oxygen, silicon or nitrogen in the ring structure. The heterocyclic monomers serve a special interest in ROMP because they bring chemical bonds (i.e., oxygen, silicon and/or nitrogen) other than the carbon into the polymer chain structure.
Both strained and unstrained cycloolefins can be used in making thermoset polymer depended on the ROMP catalyst system and the reaction conditions. The bicyclic olefin, polycyclic olefin and heterocyclic monomer may have a strained cycloolefin structure. The strained cycloolefins used in the ROMP reaction typically are Diels-Alder adducts of cyclopentadiene.
Suitable Diels-Alder adducts have the formula I:

Where R1 and R2, each independently of the other, are hydrogen, C1-C12 alkyl, C1-C12 alkene phenyl, tolyl, cyclohexyl, cyclohexenyl, halogen, cyano, C1-C12 hydroxyakyl or C1-C12 haloalkyl, or R1 and R2 together with the linkage carbon atoms are a five- or six-membered ring.
The most common Diels-Alder adducts of cyclopentadiene are: dicyclopentadiene (DCPD), norbornene, norbornadiene, cyclohexenyinorbornene, tetracyclododecene, 5-ethylidene-2-norbornene (ENB) and methyltetracyclododecene. Polycyclic olefins are made by further reacting the strained cycloolefins with cyclopentadiene through Diels-Alder reaction. The thermoset polymer can be formed by ROMP reaction when the monomer mixture of cycloolefins contains bicyclic or polycyclic olefin with multiple unsaturations. DCPD in particular is commonly used as the monomer to make thermoset polymers in a reaction injection molding (RIM) process. The DCPD monomer mixture may also contain other cyclic unsaturated compounds as a way to modify the properties of the thermoset polymer. Other types of cycloolefins contain multiple unsaturation including cyclopentadiene trimer, tetramer and higher oligomers. U.S. Pat. No. 4,703,098 describes a crosslinked copolymer comprising about 40 to 95% by weight DCPD and about 60 to 5% by weight of higher cyclopentadiene oligomers.
Another approach to make cycloolefin monomers useful for making thermoset polymers is by adding multiple strained and unstrained cycloolefins onto a molecule. Japanese Patent No. 63-092625 discloses a monomer from the Diels-Alder reaction of a 1:1 molar ratio of 3a, 4, 7, 7a-tetrahydroindene with cyclopentadiene. The monomer is useful in the ROMP reaction to produce cross-linked polymer. Japanese Patent No. 63-235324 discloses a molding product with excellent heat resistance and chemical resistance by a ROMP reaction of an ester norbornene derivative with an optional cycloalkene. The optional cycloalkene in the monomer mixture is at most 50 mol %. The ester norbornene derivative is a Diels-Alder reaction product of ester with 1 to 4 carboxylate ester groups and 1 to 4 carbon-carbon double bonds with cyclopentadiene. The ester norbornene derivative contains 1 to 4 norbornene groups from the Diels-Alder reaction without any residual carbon-carbon double bonds. Japanese Patent No. 64-56723 discloses a crosslinked polymer molded product from the ROMP reaction of a monomer mixture containing a metathesis polymerizable cyclic compound and esters from the norbornene ring-containing carboxylic acid and norbornene ring-containing alcohol.
U.S. Pat. No. 5,143,992 describes cyclopentadiene adducts of a cyclic hydrocarbon compound of up to 20 carbon atoms containing two vinyl groups as substituents on carbon atoms at least one carbon atom apart on an aliphatic ring system of from 5 to 10 carbon atoms and of 1 ring or 2 fused rings. WO 97/32913 describes a solvent free polymerizable composition comprising a Diels-Alder adduct of unsubstituted or substituted cycloolefins and unsubstituted or substituted 1, 3-cyclopentadienes having a low content of residual unsubstituted or substituted 1,3-cyclopentadienes. The molding product made with the solvent-free polymerizable composition by ROMP reaction was claimed to have good mechanical (physical) properties.
The thermoset molding composition may contain fibers, filler, reinforcing agents or other additives to adjust or enhance the molding properties. U.S. Pat. Nos. 5,939,504 and 6,310,121 describe the inclusion of an electron donor or Lewis base in the resin composition to change the rate of cycloolefin metathesis catalyzed by ruthenium or osmium carbene complex catalyst. U.S. Pat. No. 7,666,966 includes a chain transfer agent represented by the formula CH2═CH-Q, wherein Q is a group which has at least one group selected from the group consisting of a methacrylol group, acrylol group, vinyl silyl group, epoxy group and amino group. The chain transfer agent is used to control the degree of polymerization in the making of a post-linkable thermoplastic resin. The post-linkable thermoplastic resin can be cross-linked at an elevated temperature at later processing stage.